Power cord and cable systems for supplying external power to a device are known to include various assemblies or parts. One end of the cord or cable may be configured with an AC plug for plugging into an AC wall outlet of a building. The electrical cord or cable system may also include an AC/DC power adapter that converts AC power to DC power, e.g. from AC current and voltage to DC current and voltage. The DC end of the electrical cable system may be fitted with an electrical connector adapted to be inserted into a socket or port of a device to provide power to the device.
At least some electrical connectors are configured with a locking mechanism. When the electrical connector is inserted into the receptacle or socket of the device, a locking mechanism latches or locks, thus preventing the electrical connector from inadvertently being disconnected from the device.
At least some devices configured to receive power from an external power supply, such as an AC wall outlet as described above, have an internal power supply, e.g. a battery. Although the battery may supply power to the device when external power is lost, a battery may also provide power when the device is used in a portable fashion. Such portable devices include laptop and/or notebook computers, handheld devices such as cell phones and personal digital assistants, and the like. Users of a portable device may purposely disconnect the device from external power when using the device in a portable fashion. However, problems may arise when disconnecting external power from a portable device that is in use.
A device in use may require some sufficient amount of time after disconnection from an external power supply to ready the internal circuitry of the device for use of an internal battery supply. Sufficient time may be provided by the AC/DC power adapter when a portable device is disconnected from external AC power at the AC wall outlet. The AC/DC power adapter typically has reserve capacitance enabling the adapter to continue supplying DC power to the device for a short interval. However, if the user disconnects the electrical connector at the device interface instead of unplugging the AC wall outlet plug, transfer from external power to internal battery power is immediate. In this case, at least some of the internal circuitry of the device may not have sufficient time to adjust to a lower power consumption mode to make ready for use of the battery. Insufficient current from the internal battery may be supplied to the internal circuits of the device during the time the circuitry is adjusting for use of the internal battery supply. The device may malfunction as a consequence.
For example, when the electrical connector is disconnected at the device, insufficient power or current from the battery may result in a corrupted image being displayed on a screen or LCD panel of the device. The corrupted image may result from a graphics device memory being corrupted due to a lack of sufficient current to the graphics device during adjustment of the graphics device to a lower power consumption level. A lack of sufficient current may result in failure of other device circuits as well. For example, a microprocessor may misinterpret an executable instruction, which may result in an application program, such as an editor, failing.
Although a locking mechanism may be provided with the electrical connector to avoid inadvertent disconnection of the electrical connector from the device, users of portable devices may desire to purposely disconnect the electrical connector from the port and use the device in a non-office location, e.g. a meeting room. As an example, the electrical connector may be configured into a docking station or apparatus that supports quick removal of the device for portable use.
One solution or approach for preventing insufficient current from an internal battery during a power mode adjustment time is to shorten the power mode adjustment time. However, due to inherent latency issues, shortening the power mode adjustment time may not be possible. For example, at least some operating systems are notified through a physical interrupt signal when external power is lost. However, an inherent latency exists for the operating system to service the interrupt and to schedule a software task that, when finally executed as determined by scheduling, lowers the power consumption mode of internal circuits of the device. Accordingly, it may not be possible to significantly shorten the power mode adjustment time required by the internal circuits of the device.
As is known in the art of operating systems, an operating system may prevent usage of a device while the device is being removed. For example, in the case of a DVD drive, a process of unlatching the DVD drive first before removal of the DVD may be required. The unlatching of the DVD drive may signal an operating system of the laptop computer that the DVD drive is about to be removed. Upon being signaled by the unlatching of the DVD drive, the operating system ceases allowing use of the DVD drive. The DVD drive may then be removed without any faults occurring due to software making use of the DVD while the DVD drive is being removed. However, the short transition time available from immediate loss of power to transitioning circuits to a power mode acceptable for receiving battery power would not allow an operating system enough time to be notified and to then notify affected circuitry.
A need exists for providing sufficient time to adjust the internal circuits of a device to a lower power consumption mode when immediately switching the device from an external power supply to an internal battery supply.